1. Field of the Invention
The present invention relates to a hydroponic plant cultivation device having a plurality of cultivation units which are vertically arranged to form a tower-like structure.
In recent years, it become gradually difficult to carry out with a reasonable efficiency a farming utilizing or basing soil, due to its inherent problems of that the soil does show a poor holding ability on chemical fertilizers, agricultural chemicals and the like to require a giving of such agents in a relatively large amount for attaining a good result in growth of a plant, that a good yield can not be expected, when a repeated cultivation of same plant will be carried out on same ground, even if various fertilizers shall be given, and that an introduction of modern farm machineries reduces concerned human labour but it does not always bring an increase in yield of the plant.
Therefore, a new type agricultural system, so-called "hydroponic cultivation" having no restriction on soil has been watched with a great interest.
2. Description of the Prior Art
A typical prior art hydroponic cultivation system has been arranged in a relatively large hothouse to carry out a large scale cultivation. Such a system has disadvantages in that an apparatus for the system is too expensive, a relatively wide space is required for installing its apparatus, and a higher skill or technical knowledge is required for maintaining and conducting the system in best condition.
In order to overcome such and other disadvantages, Vincent P. Carl proposes in his U.S. Pat. No. 4,255,896 a compact hydroponic cultivation device, wherein a plurality of horizontal ducts are arranged in a triangular form in vertical section of the device, each of said ducts forming a flow path of a nutrient liquid and having planting cups which are detachably mounted thereto for supporting an inert media and a plant to be cultivated by the nutrient liquid.
Further, Ernst H. S. Sjostedt et al disclose in their U.S. Pat. No. 4,245,433 a system for regulating a pH value of a nutrient liquid which is to be circulated to cultivate a plant.